Print hammer control apparatus



NOV. 15, 1966 E, G, RlCHTER PRINT HAMMER CONTROL APPARATUS Filed NOV. 14, 1963 8 6 m m .H u y 4 m m k 7 V V m m 2 7 C ,6 d OW7/ O w 6 A A m 4 un Dn 6 w w L m m H 2 6 ,8 .z 6 m w w H L v 4 R R A* 5 NL w A R R 2 D D 5 I N VFNTOR.

EUGENE 6. R/HTEI? AroH/VEY United States Patent O 3,285,165 PRINT HAMMER CONTROL APPARATUS Eugene G. Richter, Lexington, Mass., assignor to Honeywell Inc., a corporation of Delaware Filed Nov. 14, 1963, Ser. No. 323,726 13 Claims. (Cl. 101-93) The present invention relates in general to new and improved printers .and in particular to high-speed printers wherein data is printed one line lat a time on a medium and wherein la separate print hammer corresponds to each data character space of the line.

Present-day high-speed printers of the type discussed above may be required to print lines having of the order of 120 character spaces, i.e. having 120 character columns. The characters in a line may typically `be spaced 0.1 inch center to center. This calls for identically close spacing of the print hammers which, upon being actuated, must make contact only with the desired character column. Ideally they print hammer actuators, which may be solenoids, are positioned -as close as possible to the print hammers and they are preferably aligned in precisely the same manner. In such an arrangement, the operating conditions are optimized and rapid hammer response may be expected upon the energization of the actuators. In practice, these conditions are rarely attainable, mainly for the reason that the windings and magnetic core material of the electromagnetic solenoid actuators cannot be sufficiently reduced in size to fit the available space.

A commonly used expedient is the interlacing of the print hammers by alternately actuating them from above and below the print line. If the print hammer actuators are miniatnrized, they may be positioned in aligned relationship above and below the print line, corresponding to the print hammers. Because of the close dimensions involved, such an arrangement is subject to cross-talk, due primarily to first-order flux fringing between adjacently positioned actuators. Since the reluctance of the fringing flux path varies depending on the energization of the actuators, this has the effect of varying the flight time interval of the actuated print hammers. As a consequence, poor print-out results because the vertical position of the printed characters with respect to the print line varies. The positioning of shielding material, using either eddy current or reluctance effects, between successive actuators has been shown to be ineffective to prevent flux fringing in such an arrangement because of the close positioning of the actuators. In fact, by providing additional flux paths, it has contributed to poor performance by retarding the response time of the print hammers.

An arrangement which avoids the close spacing of the actuators is shown in Patent No. 3,090,297 by Robert E. Wilkins et al., which is assigned to the assignee of the present application. Here, in order to gain space, the solenoid actuators .are positioned relatively far from the print hammers while fanning outward in a radial direction. This arrangement requires either an additional link between the `actuator and the print hammer or an armature extension. In any event, it increases the possibility of mechanical jitter between the actuato-r and the print hammer so as to' make the response of the latter less predictable to the detriment of satisfactory print-out.

It is the primary object of the present invention to provide a high-speed printer wherein the foregoing disadvantages arer overcome.

It is Vanother object of the present invention to provide a high-speed printer wherein, despite the close spacing of the print hammer actuators, the flight time interval of the print hammers is maintained constant within acceptable tolerances.

"ice

It is a further object of the present invention to provide a high-speed printer having closely positioned print hammer actuators wherein a substantially constant delay in the print hammer flight time interval is provided.

The novel features of the invention as well as further objects and advantages thereof will become apparent from the following detailed specification with reference to the accompanying drawings in which:

FIGURE 1 illustrates the pertinent portions of a highspeed printer;

FIGURE 2 illustrates the flux linkage between adjacently positioned print hammer actuators;

FIGURE 3 illustrates one embodiment of the present invention for compensating for variations of the flight time interval of the print hammers; and

FIGURE 4 illustrates another embodiment of the invention for compensating for flight time interval variations.

By way of example, FIGURE l illustrates an on-thefly printer wherein a continuously rotating print roll 28 has adjacent columns of characters embossed thereon, so arranged that all the characters rotate past the print station in each column during one revolution of the print roll. The characters are positioned so that identical characters form axially parallel rows on the surface of the print roll. As each character row passes the print station, all the print hammers 26 of those columns which contain the particular character called for, are simultaneously actuated. Printing occurs by driving an inked ribbon against a paper web both of which are stationed between the print roll and the hammers, but are not shown in the drawing. Each revolution of the print rollv 28 causes all the characters to pass the print station so that an entire line may be printed during this interval. Thereafter the paper web is advanced to the next line position where printing is called for.

In the arrangement shown in FIGURE l, the print actuators are seen to be sufficiently small to be capable of being positioned side by side in the same manner as the interlaced print hammers. Each actuator comprises a flat magnetic core 10 having a pair of legs 12 and 14, which carry series-connected main core windings 16 and 18 respectively. An armature 20, shown in its normal position, is adapted to rotate about the pivot pin 22 when it is attracted to the core 12 in response to the energization of the windings 16 and 18. When the armature is so attracted, the striker portion 24 moves forward to propel the corresponding print hammer 26 against the print roll 28 which rotates in the direction of the arrow shown. The hammer is returned by spring means (not shown) to move the armature to its normal rest position, as determined by a backstop 25 which may include damping means. In operation, a paper web and an inked ribbon are positioned between the hammers 26 and the print roll 28 so that an imprint is produced by the print hammer movement. Each print hammer actuator, including those positioned above whose armature strikerportions are interlaced with those of the print actuators positioned below, operates in the same manner.

As pointed out above, an arrangement such as that shown in FIGURE 1, is subject to flux fringing between adjacent actuators because of the close spacing involved. It will be noted that the distance D between the arma-ture 20 and the pole faces at the core legs is comparable to the spacing D between the coils of adjacent actuators. These distances may be of the 4onder of .01 to .02 inch, it being understood that D varies sin-ce the armature in its rest position is only approximately parallel to the plane of the pole faces. FIGURE 2 illustrates the flux linkage is broken lines. As shown in connection with the actuators 30, 32 and 34 and their corresponding yarmatures 30', 32

are permissible. the llight time interval are also subject to variation, the

and 34', upon the energization of the actuator 32 the major portion of the ux` flows 'from the core of the .actuator 32 to the armature 32 and vthen back to the actuator core. A smaller but significant fringing portion links the actuators 30 and 34 respectively if the latter are not energized, so as to produce a constant llux loss. This results in a decrease of the force available to propel the corresponding print hammer toward the print roll and hence in a del-ay of the flight time interval. Under actual operating conditions, the no-rmal ight time interval of the print hammer may be of the order of 1.4 milliseconds. The total delay introduced in the flight time interval by ilux loss due to flux linkage of each adjacent actuator may be of the order of 60 microseconds, or a total of 120 microseconds.

If the delay were constant `and if .a total delay of 120 microseconds can be tolerated, or if the actuator energization can be increased to compensate for the delay, it would merely be necessary to take this factor into consideration in the design parameters. The problem is, however, complicated by the fact that the delay is not constant. This is illustrated in FIGURE 2, in connection with the actuators 36, 38 and 40, which are assumed t-o be simultaneously energized. As previously mentioned, if the same data character is to be printed more than once in a given print line, the corresponding print hammers are simultaneously actuated when the proper character row rotates into printing position. This means that adjacent print actuators must be simultaneously energized so that the relationship of the fringing fluxes is altered.

In the instant case, the rfringing flux of the actuator'38, which would normally link the actuator 36, is bucked by an equal but oppositely directed flux. Similarly, the fringing flux of the actuator 38, which would normally link the actuator 40, is opposed by a flux of equal magnitude, but oppositely directed. As a consequence, the actuator 38 has no flux loss with respect to the adjacently positioned actuators 36 and 40, all the flux being available to drive the armature 38'. This results in a decrease of the flight time interval of the latter by 120 microseconds if both adjacent actuators are simultaneously energized with the actuator 38, or a decrease of 60 microseconds if only one of the actuators is simultaneously energized.

Since the print roll 28 rotates at constant velocity, the decrease in the ight time interval will produce a vertical displacement of the printed character with respect to the print line. With a print speed of the order of 800 lines per minute, a 7-microsecond change in the flight time interval results in l-mil displacement yor" the printed character with respect to the print line. The maximum tolerable displacement .-may be of the order of 5 mils, which means that flight time Ainterval variations up to 35 microseconds However, since other factors alecting allowable change of the ilight time interval due to flux fringing may only be of the order ofl 15 microseconds. As previously pointed out, cross-talk due to flux fringing cannot be eliminated by the use of magnetic shielding material between adjacent actuators unless the actuators are spaced lmuch further apart. For `a spacing corresponding to the spacing of alternate print hammers, i.e. of the order of .02 inch center-to-center, such shielding is ineffective and, in fact, it adversely alfects performance.

FIGURE 3 illustrates a circuit for maintaining the ight time interval delay substantially constant, regardless of whether or not the adjacently positioned print hammer actuators are energized. Each of the actuators A, B and C in FIGURE 3 is seen to contain a pair of -likepoled main core windings connected in series for energization from the output terminals of a corresponding p-r-int hammer vdriver circuit. These driver circuits `are ,designated by the reference numerals50, 60 and 70 respectively in FIGURE 3, the corresponding main windings being pensating winding 66 is seen to be connected/in series betweenl the negative output terminal of the driver 60 and the main winding 64 and is physically positioned on the core of the actuator C. It is poled in the opposite sense from the main windings 72 4and 74, as seen from the dot notation employed. Similarly, a compensating winding 68 is connected in series between the positive terminal of the driver 60 and the main winding 62 and is physically positioned on the core ofthe actuator A. Again, the compensating winding 68 is poled in the opposite sense as the main windings 52 and 54.

The core of the actuator B, which carries the main windings 62 and 64, additionally contains a compensating winding 56 which is poled in Iopposition to the last-recited energizing windings and which is connected in seriesl between the negative output terminal of the driver 50 and the energizing winding 54. A compensating winding 78 is also positioned on the core of the actuator B and is poled in the opposite sense as the windings 62 and 64. The compensating windings 78 is connected in series between the positive terminal of the driver 70 and the main wind-ing 72.

In the manner outlinedvabove, the actuator C includes a compensating winding 88 which is poled in the opposite sense to its main windings and which is, in turn, energized from the subsequent actuator adjacent to the actuator C. Also, the subsequent actuator carries a compensating winding which is `responsive to the energization of the actuator C. Similarly, the actuator A carries a compensating winding 46 which is poled in the opposite sense to its main windings and which is, in turn, energized from the preceding, adjacently positioned actuator. The latter actuator will also carry a compensating winding that is energized from the actuator A.

In order to illustrate the operation of the circuit, let it be assumed that the actuators A, B and C correspond respectively to the actuators 30, 32 and 34 in FIGURE 2. Thus, the actuator B only is energized whereas the actuators A and C are not. Current then ows only in the circuit connected between the positive and negative terminals of the driver 60 to energize the windinws 68, 62, 64 and 66. The compensating windings 56 and 78, which are positioned on the core of the actuator B, remain unenergized. The resultant flux in the core of the actuator B is thus due only to the energization of the main windings 62 and 64. The energy available for propelling the print hammer- 26 against the print roll 28 will, however, be decreased by a fixed amount due to the fringing of the ilux from the actuator B to the actuators A and C respectively. A predetermined delay is thus imposed on the Hight time intervals of the hammer.- -The eifect of the `energized compensating windings 68 and 66 in the actuators A and C respectively is negligible for present considerations.

Let it now be assumed that the actuators A, B and C are simultaneously energized, as illustrated in connection with the actuators 36, 38 and 40 in FIGURE 2. As pointed out above, there will be substantially zero ux fringing between adjacently positioned actuators because of the bucking eiect of the fringing fluxes under these conditions. The resultant energy available for driving the print hammer ofthe actuator B is now determined by the flux produced by the main windings 62 and 64, as well as by the opposing iluX due to the compensating windings 56 and 78 which are simultaneously energized. The turns ratio of each of the compensating windings to the main windings is such that the bucking effect compensates for the absence of the fringing iluX 'in each case.

It will be understood that the principles of the operation are similarly applicable if only one of the two adjacent actuators is simultaneously energized with the actuator B. Thus, if the actuators A and B become active at the same time, the flux linkage between B and C produces a delay in the flight time interval of a magnitude one half that when A and C are both inactive. The remainder of the viixed delay interval is, however, provided by coupling a signal of the opposite sense to the core of the Iactuator B by way of the compensating winding S6 which is energized from the actuator A. Accordingly, the delay of the flight time interval of the print hammer of actuator B remains constant.

The previous discussion dealt primarily with the effect on the operation of the actuator B which results from the energization or non-energization of the adjacent actuators A and C. It will be clear that the effect of actuator B on the operation of actuators A and C respectively, when simultaneously energized with the latter, must also be compensated for. In the case of actuator A, such compensation is effected by means of the winding 68 which applies a signal in the opposite sense to actuator A from that applied to the main windings 52 and 54. Such a compensating signal is applied only when the actuator B is energized, the turns ratio of the winding 68 to windings S2 and 54 being such that compensation is effected for the absence of the delay interval which normally prevails with respect to the flight time of the print hammer of actuator A when the actuator B is not energized.

A similar compensating signal is applied to the actuator A by way of the compensating winding 46 in response to the energization of the preceding actuator. If A were the first actuatorin line, flux fringing to the subsequent actuator only must be considered. Thus, while two windings are provided in the interest of actuator interchangeability, only the compensating winding 68 would be energized. The foregoing discussion similarly applies to the actuator C which has a compensating signal applied to it by way of the winding 66 in response to the energization of the actuator B. If C is the last actuator in line, only its compensating winding 66 will be energized.

If the print hammer actuatorsare small, the provision of a pair of compensating windings on each core could materially increase thecost of manufacture. In the embodiment of the invention which is illustrated in FIGURE 4, this problem is avoided by coupling compensating signals to the adjacent drivers through RC coupling circuits. As before, the arrangement isillustrated by means of three actuators, applicable reference numerals having been carried forward from FIGURE 3. It will be noted that the positive output terminal of the driver v60 in FIGURE 4 is RC-coupled to the negative output terminal of the driver 70, as well as to the negativeoutput terminal of the driver 50 by means of coupling circuits 66 and 68 respectively. Similarly, the positive output terminal of the driver 50 is RC-coupled to the negative terminal of the driver 60 by means of an RC-coupling circuit 56', while the positve output terminal of the driver 70 is coupled to the negative output terminal of the driver 60 by means of an RC-coulpling circuit 78. In like manner, RC circuits couple the positive and negative terminals of the drivers 50 and 70 to the preceding and subsequent actuators respectively.

Compensation for variations of the delay in the ight time interval is eifectedin the embodiment of FIGURE 3 throughthe RC-coupling circuits. These circuits introduce compensating signals that affect the flux-time charactcristic of each energizing circuit so as to compensate for the decrease in the delay due to the energization of the adjacent actuators. More specifically, when the actuators A and B are simultaneously energized, the coupling circuit 56 provides a signal which causes the ux produced by the main windings 62 and 64 of actuator B to decrease suiciently to compensate for the change in ux loss due to the energization of the actuator A. Conversely, the RC compensating circuit 68 introduces a signal into the energizing circuit of the actuator A to compensate for the decrease in flux loss due to the energization of the actuator B.

actuator C. Similarly, the actuator C, is compensated for flux-time changes due to the energization of the actuator B by a signal coupled thereto by way of the RC- circuit 66.

The invention is not limited to the embodiments disclosed, but may find application in various types of printers in which it is desired to maintain the operating conditions of the respective print hammers constant under conditions where cross-talk between the respective print hammer actuators is unavoidable. It will be apparent that the embodiment of a high-speed printer shown in FIG- URE l is representative only. For example, the invention may be used in a printer wherein the print roll 28 merely serves -as a platen and the characters are embossed on the respective print hammers. Nor is the flyinghammer construction shown essential and the striker portion of the armature 20 may itself constitute the print hammer. The invention is also applicable to other types of printers, such as `chain printers or the like, wherein cross-talk between adjacently positioned actuators exists so that flux-time characteristic of each varies in a manner dependent upon the simultaneous energization of the adjacent actuator.

It will also be apparent that circuits different from those shown may be employed for coupling compensating signals between adjacent actuators. It is important to bear in mind, however, that the purpose of the compensating signals is to restore the flux-time characteristic of the compensated actuator to the same delay conditions that would prevail if the adjacent actuator were not simultaneously energized. In other words, the effect of the flux loss due to each adjacent actuator must be maintained constant.

From the foregoing disclosure of the invention, it will be apparent that numerous modifications, changes and equivalents will now occur to those skilled in the art, all of which fall within the true spirit and scope contemplated by the invention.

What is claimed is:

1. An on-the-liy printer comprising a print roll having rows of characters columnarly adapted to rotate past a plurality of adjacently positioned, aligned print hammers, a like plurality of correspondingly positioned print hammer actuators each including a magnetic core carrying a winding and a movable armature adapted to propel a print hammer against said print roll upon the application of an energizing signal of a predetermined sense to said winding, said armature being normally spaced from said core a distance comparable to the spacing between adjacently positioned actuators, :and means corresponding to each of said actuators and responsive to the signal applied thereto for energizing the adjacently flanking pair of actuators with signals of substantially the opposite sense.

2. A printer comprising a plurality of adjacently positioned, aligned print hammers adapted to produce imprints on a paper web, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said :actuators including a magnetic core carrying a winding and a movable armature adapted, upon the selective application of an energizing signal to said winding, to propel a corresponding print hammer against said paper web during a predetermined flight time interval, the normal spacing of said armature from said core being comparable to the spacing between adjacently positioned actuators so that a portion of the flux induced in said -core produced by said energizing signal links the adjacent actuators when the latter are not energized to introduce a predetermined delay in the flight time interval of said print hammer, and means corresponding to each of said actuators for inducing a ux in the core thereof in response to each energizing signal applied `to an adjacent actuator in a manner to compensate for any change of said predetermined `delay due to the presence of flux in said adjacent actuator.

3. A printer'comprising a plurality of adjacently positioned, aligned print hammers :adapted to produce imprints on a paper web, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said actuators including a magnetic core carrying a winding and a movable armature adapted to propel a print hammer against said paper lweb upon the application of a flux-inducing energizing signal to said winding, and means responsive ot the signal applied to the winding of each individual :actuator for partially energizing the windings of adjacently positioned actuators to compensate for changes in llux loss in said individual actuator.

4. A printer comprising a plurality of adjacently positioned, aligned print hammers adapted to produce imprints on a paper web, a like plurality of :actuators correspondingly positioned in close proximity to each other, each of said actuators including a magnetic core carrying a winding and =a movable armature adapted to propel a print hammer against said paper web upon the application of an energizing signal of one sense to said winding, and means corresponding to each of said actuators responsive to the signal applied to the winding thereof for partially energizing the windings of the pair of immediately adjacent actuators with compensating signals of substantially the opposite sense.

5. A printer comprising a plurality ot adjacently positioned, aligned print hammers adapted to produce imprints on a paper web, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said actuators including a magnetic core carrying a winding and a movable armature adapted, upon the selective application of an energizing signal of one sense to said winding, to propel a corresponding print Ihammer against said paper web during a predetermined flight time interval, the normal spacing of each armature tf'rom its corresponding core being comparable to the spacing Ibetween adjacently positioned actuators so that a portion of the lux induced in said core -by said energizing signal links the adjacently flanking pair of actuators to introduce, when the windings of the latter Iare not energized, a predetermined delay in the flight time of the print hammer corresponding to said core, and means responsive to each energizing signal of said one sense applied to the windings of the actuator intermediate said flanking pair of actuators to couple `a signal of substantially the opposite sense to said ilanking pair of actuators adapted to cornpensate [for any decrease `ot said predetermined delay `due to the presence of llux Iin said flanking pair of actuators.

6. In a high-speed printer having a plurality ott a-djacently positioned, aligned print hammers tor striking selected characters of a corresponding plurality of character columns disposed on a rotating print rolll opposite said hammers to form imprints on an intermediately positioned paper web, a plurality ot adjacently positioned,

aligne-d Kactuators corresponding respectively to said print hammers, each of said actuators including a magnetic core carrying an actuator winding, a print hammer, a movable armature responsive .to actuation .by said core to propel said print hammer against said print roll during a predetermined llight time interval, the spacing of said armature trom said core 'being comparable to the spacing between Iadjacent actuators, means for applying energizing signals of one polarity to said actuator windings, and means correspon-ding to each actuator `for compensating for flight time variations `due to changes of flux linkages between adjacent actuators, said last-recited means bein-g a respons-ive to input signals applied to the winding of an actuator to energize a pair of adjacently anking actua- ,tors in the opposite sense.

7. A printer comprising a plurality of adjacently positioned, aligned pri-nt hammers adapted to-produoe imprints on a paper web stationed in iront of a support, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said lactuators including a magnetic core carrying a main winding and a movable armature adapted to propel a print hammer against said paper web .upon the application of an energizing signal ot one polarity to said main winding, and a pair of compensating windings connected in series with each of said main windings, each of said compensating windings being disposed on the core of an adjacently positioned actuator for partial energization by a signal of a polarity opposite to said one polarity. v

8. A printer comprising Ia plurality of adjacently positioned, aligne-d print hammers adapted to produce irnprints on a paper web stationed in rfront of a support, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said actuators including a U-sh-aped magnetic core having a pair of likepoled, series-connected energizing windings disposed on the legs ot said core, a movable armature disposed across v the open portion of said core for propelling a print hammer against said paper web upon the appli-cation of an energizing signal to said windings adapted to induce a tlux of one polarity in said core, the normal spacing of said armature from said core .being comparable to the spacing .between adjacent actuators to cause said il-ux to link t-he latter, each ofsaid pairs of energizing windings having a pair of compensating windings connected in series therewith disposed on the cores of adjacently flanking actuators, `the compensating windings connected to actuators adjacent to .bo-th sides of each intermediately positioned core being adapted, when energized, to induce a llux ot a polarity opposite to said one polarity in the latter core to compensate `for changes in flux loss due to the energization of said adjacent actuators.

9. A printer comprising a plurality of adjacently positioned, aligned print hammers adapted to produce imprints on a paper -web stationed in front of a support, a like plurality of actuators correspondingly positioned in close proximity .to each other, each of said actuators including a magnetic core carrying a winding and Ia movable armature adapted to propel a print lhammer against said paper web upon the application of an energizing signal to said winding, and a compensating circuit coupled between eac'h terminal off a given polarity of said winding on each actuator to a terminal ot the opposite polarity of the winding belonging to an adjacently positioned actuator adapted to compensate for changes in flux loss due to the energization of said adjacent actuator.

10. A prin-ter comprising Ia plurality of adjacently Ipositioned, aligned print hammers adapted to produce i m,

prints on a paper we'b stationed in lfront of a support, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said actuators including a magnetic core carrying 4a winding and a movable armature adapted to propel a .print hammer against said paper web upon the application of -a linx-inducing signal -to said Winding, and a pair of RC circuits connected between each of said windings and the windings of anking actuators disposed to both sides thereof for coupling signals to the actuator intermediate said anking yactuators ladapted to offset changes in flux loss of said intermediate actuator due to the4 energiz-ation of said flanking actuators.

11. A printer comprising a plurality of adjacently posiltioned, aligned plint hammers adapted to produce imprints on a paper web stationed in rfront of a support, a like plurality of actuators correspondingly positioned in close proximity to each other, each of said actuators including a U-shaped magnetic core having a pair od like-poled energizing windings disposed on the legs ot said core connected in series between a pair of input terminais, a movable armature disposed across the open portion of said core for propelling a print hammer against said paper web upon the application of -a flux-inducing energizing signal to said terminals, the normal spacing of said armature from said core being comparable to the spacing between adjacently positioned -actua-tors to cause said llux to link said adjacent actuators, a pair 4of RC circuits coupling each terminal 'of a terminal pair corresponding to an intermediately positioned actuator to oppositely poled terminals associated with actuators which adjacently ank said intermediately positioned actuator, said RC circuits being adapted to couple signals to said intermediately positioned actuator to compensate for changes in flux loss due to .the energization of said adjacently ankin'g actuators.

1,2. A high speed printer comprising a plurality orf adjacently positioned, aligned print ham-mers for striking selected characters of a corresponding plurality of character columns disposed on a rotating print rol-l opposite sai-d hammers to 'form [imprints on an intermediately positioned paper web, a plurality ot adjacently positioned, aligned actuators corresponding respectively to said print hammers, each of said actuators including a magnetic U-core h'aving a pair of like-poled series-connected .actuator windings each disposed on one core leg, a movable armature positioned across the open end of said U-core and adapted, upon the activation of said actuator, to propel the corresponding hammer against said print roll during a predetermined ilight time interval, the normal spacing ot" said armature :from said U-core being comparable to .the spacing between adjacent actuators, -means for simultaneously energizing said actuator windings of selected ones of said actuators, the tringing flux from each orf said U-cores Whose actuator windings are energized linking the adjacently flanking pair of U-cores to introduce a predictable -delay in said ilight time interval when the actuator windings of said anking U-cores are not energized, and a compensating winding disposed on each core legs of each actuator each connected in series wlith the actuator windings of one orf the adjacently flanking pair of actuators, each of said compensating windings being poled in opposition to the actuator windings on the same core to maintain said delay constant when the actuator windings of adjacently flanking actuators are energized simultaneously with the windings of the actuator positioned therebetween.

13. A high-speed printer comprising a plurality of adjacently positioned, aligned print hammers for striking selected characters ot a corresponding plurality of character columns disposed on a rotating print roll opposite said hammers to form imprints on an intermediately positioned paper web, a plurality of adjacently positioned, aligned actuators corresponding respectively to said print Ihammers, eachI of said actuators including a magnetic U-core having a pair of like-,poled windings connected in series between a .pair of input terminals and each' disposed on one core leg, -a mova'ble armature positioned across the open end of said U-core and adapted, upon the activation of said actuator, to propel the corresponding hammer against said print roll during a predetermined flight time interval, the normal spacing olf said armature from said U-core being comparable to the spacing between adjacent actuators, means for simultaneously energizing the windings of selected ones of said actuators, the fringing flux from each of said U-cores whose windings are energized linking the adjacent pair of U-cores to introduce a predictable delay in said ight time interval when the windings of said adjacent U-cores are not energized, and an RC circuit coupled between each terminal of an input terminal pair corresponding to an intermediately posi- Itioned actuator and oppositely polled termin-als associated with actuators which adjacently flank said intermediately positioned actuator Ifor coupling signals therebetween in order to maintain said `delay constant when said adjacently anking actuators are activated simultaneously with said intermediately positioned actuator.

References Cited by the Examiner UNITED STATES PATENTS 2,907,986 10/1959 Rajchman 317-123 X 3,001,469 9/1961 Davis et al. lOl-93 3,049,990 8/1962 Brown et al lOl-109 X 3,129,419 4/1964 Clark et al 317-134 X ROBERT E. P ULFREY, Prz'mmy Exwmner.

P. R. WOODS, Assistant Examiner. 

1. AN ON-THE-FLY PRINTER COMPRISING A PRINT ROLL HAVING ROWS OF CHARACTERS COLUMNARLY ADAPTED TO ROTATE PAST A PLURALITY OF ADJACENTLY POSITIONED, ALIGNED PRINT HAMMERS, A LIKE PLURALITY OF CORRESPONDING POSTIONED PRINT HAMMER ACTUATORS EACH INCLUDING A MAGNETIC CORE CARRYING A WINDING AND A MOVABLE ARMATURE ADAPTED TO PROPEL A PRINT HAMMBER AGAINST SAID PRINT ROLL UPON THE APPLICATION OF AN ENERGIZING SIGNAL OF A PREDETERMINED SENSE TO SAID WINDING, SAID ARMATURE BEING NORAMLLY SPACED FROM SAID CORE A DISTANCE COMPARABLE TO THE SPACING BETWEEN ADJACENTLY POSITIONED ACTUATORS, AND MEANS CORRESPONDING TO EACH OF SAID ACTUATORS AND RESPONSIVE TO THE SIGNAL APPLIED THERETO FOR ENERGIZING THE ADJACENTLY FLANKING PAIR OF ACTUATORS WITH SIGNALS OF SUBSTANTIALLY THE OPPOSITE SENSE. 